Metastasis to the brain is a clinical problem in patients with breast cancer (1-3). We mined published microarray data (4, 5) to compare primary and metastatic tumor transcriptomes for the discovery of genes associated with brain metastasis in humans with metastatic breast cancer. We found that the transmembrane protein 134, encoded by TMEM134, was among the genes whose expression was most different in the brain and lymph node metastases of patients with metastatic breast cancer. TMEM134 mRNA

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... s present at increased quantities in brain metastatic tissues as compared to primary tumors of the breast. Importantly, expression of TMEM134 in primary tumors was significantly correlated with patient overall survival in patients with breast cancer. Modulation of TMEM134 expression may be relevant to the biology by which tumor cells metastasize from the breast to the brain while evading immune clearance in the lymph nodes in humans with metastatic breast cancer. These data are one piece of evidence suggesting a common ancestor or tumor clone for brain and lymph node metastases that originate from the primary tumor, alluding to patterns in developmental origin and migratory pathways through the lymph node in human brain metastatic breast cancer.